Mailbox insert sleeve



FIG. 1 is a front, top and side perspective view of the mailbox insert sleeve showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a side elevational view thereof, the side opposite being a mirror image of the side shown in FIG. 4;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof. 

The ornamental design for a mailbox insert sleeve, as shown and described. 